A rim (5) for a bicycle wheel having a body (20) with a substantially annular extension with a radially outer portion (22) shaped for coupling with a tire is disclosed. The radially outer portion (22) has a hole (39) for an inflation valve. The radially outer portion (22) also includes, at the hole (39) and/or in an area proximal to the hole (39), at least one cross section having a different shape from that at an area distal from the hole, so as to form at least one second surface discontinuity (35) along the annular extension of the radially outer portion (22). The second discontinuity (35) makes it easier to assemble to wheel and allows an optimal coupling to be made between the rim (5), inflation valve, and tire, in the case of a tubeless wheel, and between rim (5), air chamber and tire, in the case of a wheel with an air chamber.